1. Field of the Invention
This invention relates to loading dock equipment and in particular to dock levelers that are used to span the distance between a loading dock and the bed of a vehicle. Specifically, it deals with a configuration for bumpers for use with a wider lip for a dock leveler that still protect the lip and the deck of the leveler from damage.
2. Prior Art
A conventional loading dock for transport vehicles typically has a dock leveler with a dock bumper placed on each side of the lip at a fixed position on the dock face. The width of the dock leveler is usually limited to a maximum width of seven feet because if the bumpers are placed wider apart then there is a risk that the vehicle may miss the bumper and strike the dock leveler when it backs into position. Some specialty dock levelers are wider than seven feet to provide space for wider than normal cargo. Examples of these devices are shown in U.S. Pat. Nos. 5,881,414 and 6,070,203. A dock leveler with the bumpers mounted rigidly on the front as described in U.S. Pat. No. 6,070,203 may be unable to raise and extend the lip. A transport vehicle may be positioned against the bumpers with sufficient force to prevent the dock leveler from raising, or the top of the bumpers may strike a door hinge or other protrusion beyond the rear of the transport vehicle. By retracting the bumpers there is no interference to raising the dock. The bumper mounting shown in U.S. Pat. No. 6,070,203 could potentially have utility with the lip that extends linearly such as shown in U.S. Pat. No. 6,081,954. The hypothetical reason is that since the lip does not rotate down in front of the leveler there is no requirement for the lip and the bumpers to occupy the same space. However if the bumpers cannot be retracted they may interfere with the transport vehicle and prevent the leveler from raising to extend the lip. Consequently such a theoretical structure still has significant shortcomings.
U.S. Pat. No. 4,420,849 shows a dock leveler with bumpers that fold away to accommodate wide loads, but with all of these devices the width of lip is limited by the space between the dock bumpers.
U.S. Pat. No. 6,081,954 describes a dock leveler with a lip that extends linearly rather than rotating in the conventional manner. However the distance between the bumpers would still limit the width of the leveler.
Given the shortcomings of the prior art, there is a need for a dock leveler which has a lip that is wider than the distance between the dock bumpers yet still provides protection to both the vehicle and the dock equipment as the vehicle backs into position. Additionally, the traditional xe2x80x9cbridgexe2x80x9d function of the leveler lip must be maintained to eliminate any gap between the vehicle and the dock leveler deck. One method of shipping cargo has two rows of wheeled carts on a transport vehicle. When a row of carts is pulled from the transport vehicle onto the loading dock, the outer wheels of the carts will extend beyond the seven foot span of a conventional dock leveler lip. Thus the wheels of the cart may fall into the gap between the back of the transport vehicle and the front of the dock bumper, and the movement of the carts may be impeded.
This invention is a dock leveler that has a lip that is wider than the space between the dock bumpers. The dock bumpers protrude through openings in the lip plate to provide protection at the same location as conventional bumpers. The protruding portion of the bumper is preferably segmented so that width of each opening in the lip is narrower than the width of the wheels of the carts. Thus the lip may be almost as wide as the opening in the back of the transport vehicle and all the wheels of the cart may roll easily from the bed of the transport vehicle over the lip and onto the dock leveler. Another feature of the bumpers is that they are retractable to allow the dock leveler to raise and extend the lip.
While a specific object of this invention is to define a leveler having a wider lip, it is also apparent that another compatible object of this invention is to define a dock leveler system with improved bumper protection for the assembly. That is, the assembly may be a conventional width.
The first preferred embodiment of this invention is described as follows. A dock leveler is mounted in a recessed pit of conventional construction. The dock leveler may be as wide as necessary to provide access to the transport vehicle. A lip is mounted to the front of the deck of the leveler and pivoted in a conventional manner. The lip may be of conventional configuration where the back edge of the lip abuts the front of the deck when extended. It may also be of the xe2x80x9cbarrier lipxe2x80x9d configuration where the rear of the lip is extended above the top of the deck to provide a run-off guard when the lip is pendent. While either lip configuration may be used with this invention, the xe2x80x9cbarrier lipxe2x80x9d configuration will provide greater strength for the lip. A series of slotted holes is cut through the lip at each bumper. The width of each opening is preferably narrower than the width of the wheels travelling over the lip. A dock bumper of special configuration is mounted under each side of the deck and has segments which protrude through the slotted holes in the lip. Thus the front of the bumpers will contact the back of the transport vehicle to provide a space in front of the lip. The bumpers are mounted so that the front face of the bumper segments may be retracted behind the front of the lip so the leveler and lip may be raised without interference with the back of the transport vehicle.
The second preferred embodiment is similar to the first except that the dock leveler has a lip that retracts linearly rather than by rotation. Because the lip does not rotate down in front of the leveler there is no requirement for the bumpers to pass through the lip in the stored position. However the leveler must still be able to raise to extend the lip onto a transport vehicle that is higher than the dock floor. The bumpers are mounted so that they may be retracted to allow the leveler to raise without interference with the back of the transport vehicle.
The third preferred embodiment has conventional bumpers fastened to a carriage which is mounted for vertical motion along guide tracks fastened to the dock wall. The bumper carriage is constructed with vertical support plates so that a wide lip with slotted openings may fit between the vertical support plates and store behind the bumpers.
Thus the bumpers do not limit the width of the lip. Because the bumpers are always under the lip when the dock leveler is in the operative position, the bumpers may be spring biased toward the upper position. This would eliminate the need of a hydraulic positioning system such as that described by in U.S. Pat. No. 6,006,389. When the transport vehicle height is at or above the height of the dock then the lip will reach over the bumpers. When the transport vehicle is lower than the dock floor, the lip will contact the top of the bumpers and force them down to the proper height. This embodiment would also work with low docks where the upper position of the bumper is higher than the dock floor. As with the first preferred embodiment, the lip may be a conventional one or a run-off guard configuration.
The fourth preferred embodiment is similar to the third except that the bumper mounting brackets are fixed to the dock wall at a height that does not exceed the height of the bed of the transport vehicle. Transport vehicles lower than the height of the bumpers may be lifted to the desired height by the use of a truck leveler or wheel riser ramps, which are well known in the industry.
The fifth preferred embodiment has conventional dock bumpers mounted directly to the dock face. As in the fourth preferred embodiment transport vehicles lower than the height of the bumpers may be lifted to the desired height by the use of a truck leveler or wheel riser ramps. A wide dock leveler of conventional construction but with a longer lip is mounted in a pit formed behind the dock wall. In the operative position the lip would reach over the dock wall and the bumpers to rest on the bed of the transport vehicle. When in the stored position the lip of the dock leveler is placed in a cavity formed in the pit behind the bumpers. This embodiment will work with dock levelers of other configurations including vertically stored with rigid or hinged lip, and horizontally stored linearly retracting lip.
This invention will be described in greater detail by referring to the attached drawing and the description of the preferred embodiment that follows.